Metathesis-curable composition with a reaction control agent

ABSTRACT

A composition curable by a metathesis reaction upon mixing its components and comprising an olefin-containing substrate, a metathesis catalyst, and a reaction control agent for slowing the progress of the metathesis reaction. The metathesis catalyst is a ruthenium or osmium carbene complex catalyst having high activity and good air stability. In one embodiment, the catalyst is free of phosphine ligands. The reaction control agent is an organic compound that contains carbon-carbon double and/or triple bonds and one or more Group 14 atoms and is present in an amount effective to slow the progress of the metathesis reaction. In one embodiment, the olefin-containing substrate may comprise one or more oligomers or polymers having a &gt;20 wt.% linear siloxane (Si—O—Si) backbone tethered and/or end-capped with functional olefin groups, such as cycloalkenyl group.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly-owned, co-pendingU.S. patent application Ser. No. 10/891,918 entitled METATHESIS-CURABLECOMPOSITION WITH A REACTION CONTROL AGENT filed Jul. 15, 2004, which isa continuation-in-part of commonly-owned U.S. patent application Ser.Nos. 10/430,592, now U.S. Pat. No. 7,060,770 issued Jun. 13, 2006 andentitled METATHESIS-CURABLE COMPOSITION WITH A REACTION CONTROL AGENT,and Ser. No. 10/430,953, now U.S. Pat. No. 6,844,409 issued Jan. 18,2005 and entitled COMPOSITION CURABLE BY METATHESIS REACTION, thedisclosures of which are incorporated herein by reference in theirentirety as if completely set forth herein below. Other commonly-ownedrelated applications include: U.S. Pat. No. 6,455,029 issued Sep. 24,2002 and entitled DENTAL IMPRESSION MATERIAL UTILIZING RUTHENIUMCATALYST; U.S. Pat. No. 6,649,146 issued Nov. 18, 2003 and entitledDENTAL IMPRESSION MATERIAL UTILIZING RUTHENIUM METATHESIS CATALYST; U.S.Pat. No. 6,861,386 issued Mar. 1, 2005 and entitled ACCELERATOR FORMETATHESIS CATALYST; and U.S. Pat. No. 7,060,769 issued Jun. 13, 2006and entitled METHOD OF CURING A COMPOSITION BY METATHESIS REACTION USINGREACTION CONTROL AGENT.

FIELD OF THE INVENTION

This invention relates to compositions that undergo a metathesisreaction initiated by a metathesis catalyst and that contain a reactioncontrol agent for controlling the progress of the metathesis reaction.More specifically, the control agent slows the progress of themetathesis reaction, and depending on the nature of the control agent,may prevent completion of the reaction until the composition is exposedto temperatures higher than the mixing temperature.

BACKGROUND OF THE INVENTION

Addition polymerizable silicone resins are widely used in many fieldssuch as electronics, health care and automotive applications. Thepolymerizable resins are cured as a two-part system using ahydrosilation reaction. A platinum catalyst is used in one part, thecatalyst side, and a hydrogen terminated polydimethylsiloxane (HPDMS) inthe other part, the base side, while both sides contain vinyl terminatedpolydimethylsiloxanes (PVDMS) resins. When these materials are cured atroom temperature, they are referred to as room temperature vulcanized(RTV). The most common RTV materials are typically offered as a 10:1ratio base/catalyst, such as RTV630 (GE Silicones), while some other RTVmaterials are offered at a 1:1 ratio, such as RTV6428 (GE Silicones).Various working times are required depending on the application from 2minutes to several hours and may involve a heat curing step aboveambient temperature. The working time is controlled with a retarder orinhibitor mixed with the catalyst component, such as an amine oracetylenic compound.

Another class of addition polymerizable silicone resins is the liquidsilicone rubber (LSR) materials prepared through the liquid injectionmolding (LIM) process. The LSR materials are cured at a temperature of120° C.-180° C. in a mold injected to after mixing. The mixture includesa retarder mixed with the catalyst component, such as an amine oracetylenic compound, which allows the hydrosilation reaction to occur atthe mold temperature only.

Both the RTV and LSR types of formulations suffer from the shortcomingsof the hydrosilation mechanism. These shortcomings include: (1)deactivation of the platinum catalyst by sulfur or other nucleophilicimpurities; (2) high shrinkage, approximately 1%, due to the highreduction of free volume upon polymerization; (3) high cost of platinummetal needed for catalysis; (4) high cost of HPDMS and PVDMS resins; (5)requirement of two different resins to be employed, namely vinyl andhydrogen terminated; (6) undesirable hydrogen evolution from thedecomposition of the hydrosiloxane cross-linkers that typically arepresent in these systems; and (7) vinyl functionalized PDMS resins havea low hydrocarbon content in the main chain after polymerization due tothe presence of only an ethyl spacer, which may lead to a relativelyhigh dielectric constant, which is an undesirable property for someelectronic applications.

A new type of polymerization system has been recently developed that maypotentially be used to replace addition-curable silicones and platinumcatalysts in a wide variety of applications to thereby avoid theshortcomings of the hydrosilation mechanism discussed above. In this newmetathesis reaction system, curing is achieved by a ring-openingmetathesis polymerization (ROMP) mechanism. Metathesis is generallyunderstood to mean the metal catalyzed redistribution of carbon-carbondouble bonds. The polymerizable composition comprises a resin systemthat includes functionalities or groups that are curable by ROMPtogether with a metathesis catalyst, such as a ruthenium carbenecomplex. However, to efficiently utilize ROMP to prepare polymers, thereis a need to control the progress of polymerization, particularly formolding applications.

In commonly-owned U.S. Pat. No. 6,649,146, a two-part room temperatureROMP-curable formulation containing siloxane polymers and fillers wasdescribed as usable as a dental impression material. The catalystsdescribed therein are ruthenium carbene complexes containing phosphineligands. These catalysts, however, are air sensitive because thephosphines can dissociate and oxidize, thereby leading to reduced shelflife. An alternative highly active ruthenium carbene complex that doesnot contain phosphine groups is described in Hoveyda et al. U.S. Pat.No. 6,921,735. This alternative catalyst has a good air stabilityprofile. However, when this alternative catalyst is substituted for thecatalysts containing the phosphine ligands, the composition exhibits avery short working time after mixing, on the order of 20 seconds, whichmakes the use of these compositions impractical in many applications,such as dental impression materials. There is thus a need to provide aroom temperature ROMP-curable formulation that has good air stability aswell as a longer working time after mixing.

In addition to ROMP, other metathesis reaction systems utilizemetathesis catalysts, for example ring closing metathesis, acyclic dienemetathesis polymerization, ring opening metathesis and cross metathesis.There is further a need for controlling the progress of reaction inthese other metathesis reaction systems.

SUMMARY OF THE INVENTION

The present invention provides a composition that upon mixing of itscomponents undergoes a metathesis reaction, wherein the compositioncontains components for controlling and catalyzing the metathesisreaction. The composition comprises a ruthenium or osmium carbenecomplex catalyst that is capable of initiating a metathesis reaction,such as ring-opening metathesis polymerization (ROMP), a reactioncontrol agent for slowing the progress of the reaction, and ametathesis-curable olefinic substrate. The catalyst may have thefollowing structure:

wherein:

M is ruthenium or osmium,

X is an alkylidene ligand with basicity higher than that oftricyclohexylphosphine (PCy₃),

X² and X³ are either the same or different and are any anionic ligand,

Z is oxygen (O) or sulfur (S), and

R⁴, R⁵, a, b, c, and d are the same or different and are each a linear,branched, cyclic or polycyclic organic residue optionally containingsiloxane groups (Si—O—Si) and optionally containing heteroatoms selectedfrom the group consisting of B, N, O, Si, P, and S.

The composition further comprises a reaction control agent, which slowsthe progress of the metathesis reaction. The control agent allows thecomposition to be cured after a certain delayed time after mixing (worktime or pot life) or allows for completion of curing only by heating totemperatures above the mixing temperature at any time during the worktime period. The control agent, and the amount thereof, also allows forcontrol of the viscosity build up rate as the metathesis reactionproceeds, which is useful for many molding applications. The reactioncontrol agent is an organic compound that contains carbon-carbon doubleand/or triple bonds and one or more central Group 14 atoms, and canfurther contain, in the case of a Si central atom, oxygen atomsconnected to the silicon to form siloxane bonds. More particularly, thereaction control agent has the following structure:

wherein:

G is selected from the group consisting of: L³,

L is a hydrocarbon fragment containing a double or triple bond,

L¹-L⁹ are each independently selected from the group consisting of L,alkyl, aryl, aralkyl or haloalkyl,

A is a Group 14 atom,

n=0-20, and

m=0-20.Advantageously, L is an allyl (2-propenyl), vinyl (ethenyl), ethynyl, orpropargyl (2-propynyl) group. Also advantageously, the reaction controlagent includes more than one L group. In an exemplary embodiment of theinvention, the reaction control agent is tetraallyl silane (TAS):

In another exemplary embodiment, the reaction control agent istetraallyloxy silane (TAOS).

The catalyst and the reaction control agent are combined with anolefinic substrate to provide a composition that undergoes themetathesis reaction with a controlled rate. In one embodiment of thepresent invention, thermal or photochemical activation, for example, isneeded to complete the metathesis reaction. In another embodiment, thecomposition comprises any cycloalkenyl-functionalized oligomer orpolymer that can undergo polymerization via ROMP. In another embodimentof the present invention, the composition comprises an olefin-containingresin system comprising one or more oligomers or polymers having a >20wt. % linear siloxane (Si—O—Si) backbone that can be tethered and/orend-capped with functional olefin groups, such as cycloalkenyl groups,that can undergo a metathesis reaction. In yet another embodiment,norbornenylethyl terminated and/or tethered polydimethylsiloxane resinsare used. In yet another embodiment, cycloolefins such asdicyclopentadiene (DCPD) can be used.

DETAILED DESCRIPTION

The present invention provides formulations of ruthenium or osmiumcarbene complexes together with reaction control agents that allowcontrol of the progress of a metathesis reaction on an olefin-containingsubstrate.

The catalysts useful in the present invention include ruthenium orosmium carbene complexes having the following structure:

wherein:

M is ruthenium or osmium,

X is an alkylidene ligand with basicity higher than that oftricyclohexylphosphine (PCy₃),

X² and X³ are either the same or different and are any anionic ligand,

Z is oxygen (O) or sulfur (S), and

R⁴, R⁵, a, b, c, and d are the same or different and are each a linear,branched, cyclic or polycyclic organic residue optionally containingsiloxane groups (Si—O—Si) and optionally containing heteroatoms selectedfrom the group consisting of B, N, O, Si, P, and S.

In one embodiment, the ring-opening metathesis activity and airstability of the catalyst can be increased by using an alkylidene ligandX, such as a saturated imidazolidine ligand, having a basicity or protonaffinity higher than that of tricyclohexylphosphine (PCy₃) ligands. Theligands X may be 4,5-dihydroimidazol-2-ylidenes, which have thefollowing general structure:

R may be mesityl (2,4,6 trimethylphenyl) and R′ may be H or phenyl.These substituted alkylidene ligands X have a basicity or protonaffinity higher than that of tricyclohexylphosphine, which is believedto contribute to the higher activity and higher air stability. By way offurther example, X may be the1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene (sIMES) ligand asshown here:

wherein Mes is mesityl (2,4,6 trimethylphenyl). Other4,5-dihydroimidazol-2-ylidenes can also be used to afford rutheniumcarbene complexes, such as the following ligands:

wherein Mes is mesityl, and Ph is phenyl. In an exemplary embodiment,the catalyst is free of phosphine ligands.

In another exemplary embodiment, the catalyst has the structure above inwhich M is ruthenium, X is an alkylidene ligand with basicity higherthan that of tricyclohexylphosphine (PCy₃), X² and X³ are halogen atoms,Z is oxygen, R⁴ is a C₁ to C₁₀ alkyl fragment, a, b, c, and d are eacheither hydrogen or a C₁ to C₁₀ alkyl or a C₁ to C₁₀ alkoxy group, and R⁵is hydrogen.

In yet another exemplary embodiment, the catalyst has the structureabove in which M is ruthenium, X is1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene (sIMES), X² and X³ arechlorine atoms, Z is oxygen, R⁴ is either isopropyl, ethyl or methyl, a,b, c, and d are each either hydrogen, ethoxy or methoxy, and Rs ishydrogen. An example of this type of exemplary catalyst (Catalyst A) is1,3-bis-(2,4,6-trimethylphenyl)-2-(imidazolidinylidene)dichloro(o-isopropoxyphenylmethylene)rutheniumhaving the following structure:

wherein R is mesityl (R⁴=isopropyl and a, b, c, and d are each H).Another example, Catalyst B, is similar to Catalyst A except that R⁴ ismethyl and c is methoxy (CH₃O). Yet another example, Catalyst C, issimilar to Catalyst A except that R⁴ is ethyl and c is ethoxy (CH₃CH₂O).Other examples for this category of catalysts, as well as the synthesisof these catalysts, are fully described in U.S. Pat. No. ,921,735 issuedJul. 26, 2005 and incorporated by reference herein in its entirety.

The composition further comprises at least one reaction control agent.After mixing of the composition components, the control agent slows themetathesis reaction, and thereby allows for an increase in the timeperiod before cure, or before the metathesis reaction proceeds tocompletion or to a desired extent short of completion. The length ofthis time period, also called work time or pot life, may be controlledby preventing completion of the reaction until the composition is heatedto a temperature above the mixing temperature, for example about 30° C.or more above the mixing temperature. Alternatively, the work time maybe controlled by exposure to light. The reaction control agent alsoallows for control of the viscosity build up as the metathesis reactionproceeds, which is useful for many molding applications. The reactioncontrol agent is an organic compound that contains carbon-carbon doubleand/or triple bonds and one or more central Group 14 atoms, and canfurther contain, in the case of silicon as the central atom(s), oxygenatoms connected to silicon to form siloxane bonds. The reaction controlagent has the structure shown below:

wherein:

G is selected from the group consisting of: L³,

L is a hydrocarbon fragment containing a double or triple bond;

L¹-L⁹ are each independently selected from the group consisting of L,alkyl, aryl, aralkyl or haloalkyl;

A is a Group 14 atom;

n=0-20; and

m=0-20.

Of the Group 14 atoms, which include C, Si, Ge, Sn and Pb, the centralatom is advantageously Si, Ge or Sn, and more advantageously Si.

In one embodiment of the present invention, G=L₃ such that the reactioncontrol agent is a tetracoordinated compound having at least onesubstituent group L that is a hydrocarbon fragment containing a doubleor triple bond. Allyl and vinyl groups are hydrocarbon fragmentscontaining a double bond, for example, and alkynyl groups, such aspropargyl and ethynyl groups, are hydrocarbon fragments containing atriple bond, for example. For the other substituent groups L¹, L², L³,if not a hydrocarbon fragment containing a double or triple bond, thenthe substituent group is an alkyl, aryl, aralkyl or haloalkyl group,which are essentially inert to the metathesis reaction. Thus, it is thehydrocarbon fragment containing the double or triple bond thatdetermines the extent of the retardation of the metathesis reaction,such that a greater number of such hydrocarbon fragments would beexpected to achieve longer working times than similar structurescontaining fewer of such hydrocarbon fragments. An exemplary inertsubstituent is the methyl group.

In the embodiment of the present invention where G is defined as:

the central atom A is Si, such that the reaction control agent containsa straight chain siloxane compound in which the ends of the chain arecapped by hydrocarbon fragments containing a double or triple bond. Thesubstituent groups within the chain (i.e., L¹, L², L⁴, L⁵, L⁶, L⁷) mayalso be hydrocarbon fragments containing double or triple bonds or maybe an inert substituent including alkyl, aryl, aralkyl or haloalkylgroups. By way of example, where A is silicon and n=O, a disiloxanecompound is formed, such as divinyltetramethyldisiloxane.

In the embodiment of the present invention where G is:

a structure is formed having a chain of single-bonded Group 14 atomswhere the ends of the chain are capped by hydrocarbon fragmentscontaining a double or triple bond. As with the previous embodiment, thesubstituent groups within the chain (i.e., L¹, L², L⁸, L⁹) may be eitherthe hydrocarbon fragment with the double or triple bond or may be aninert alkyl, aryl, aralkyl or haloalkyl group. Where m=2, for example, a3 atom chain is formed with 2 hydrocarbon fragment double or triple bondend groups and 6 L¹-L⁹ substituent groups.

Combinations of two or more reaction control agents are contemplated bythe present invention. For example, a mixture of agents may be used,each affording different viscosity build-up characteristics. By way offurther example, one reaction control agent may be used that slows orprevents curing of the composition in the absence of heat, while asecond reaction control agent is used that slows or prevents curing inthe absence of light.

The composition further comprises an olefin-containing substrate(compound or mixture of compounds), such as a cyclic olefin-containingcompound or mixture of compounds or an acyclic olefin-containingcompound or mixture of compounds, which undergoes a metathesis reaction,such as ROMP, when mixed with the ruthenium carbene complex. Theprogression of the reaction is controlled by the at least one reactioncontrol agent, such as tetraallyl silane (TAS) or tetraallyloxysilane(TAOS), to increase the working time of the composition and to controlthe viscosity build up. In one exemplary embodiment of a compositioncurable by ROMP, the resin system comprises at least one cyclic olefinfunctionalized >20 wt. % linear siloxane (Si—O—Si) backbone oligomer orpolymer that is telechelic, tethered, tri-functional and/orquadri-functional. More specifically, the compound or mixture ofcompounds curable by ROMP may comprise one or a combination of thefollowing: a polymerizable telechelic siloxane-based polymer end-cappedwith an olefin group curable by ROMP; a polymerizable siloxane-basedpolymer tethered and end-capped with an olefin group curable by ROMP; apolymerizable tri-functional siloxane-based oligomer or polymerend-capped with an olefin group curable by ROMP; and a polymerizablequadri-functional siloxane-based oligomer or polymer end-capped with anolefin group curable by ROMP. The olefin groups may be cycloalkenylgroups, for example norbornenyl or norbornenylethyl groups.

By way of example and not limitation, one category of oligomers and/orpolymers that may be used in compositions of the present inventioninclude telechelic (end-functionalized/end-capped) polymers with any ofa variety of backbones comprising a >20 wt. % linear siloxane as long asthe chain ends are functionalized with reactive olefin groups, such ascycloalkenyl groups. For example, the resin may be a telechelic PDMSterminated with NBE groups according the following structure:

where n=5-5000, for example 27-1590. Other examples of telechelicpolysiloxanes are those having the following structure:

where n=5-5000, such as 27-1590;

R₁, R₂═C₁-C₁₈ hydrocarbon or

where R₃, R₄═H or C₁-C₁₈ hydrocarbon, and m=1-10; and

X═CH₂, S, O

R₅═C₀-C₁₈ hydrocarbon

R₆═C₀-C₁₈ hydrocarbon

Another category of oligomers and/or polymers that may be used incompositions of the present invention include oligomers or polymerscomprising a >20 wt. % linear siloxane backbone tethered and end-cappedwith groups curable by a metathesis reaction, such as cycloalkenylgroups. The oligomers or polymers may have any of a variety ofsiloxane-based backbones, particularly PDMS, with pendant groupsincorporated within the backbone or main chain that protrude therefromthus forming the tethered structure. As with the telechelic polymers,the chain ends are functionalized or capped with reactive olefin groups,such as cycloalkenyl groups, for example norbomenyl or norbomenylethylgroups. The pendant groups may also be cycloalkenyl groups, such asnorbomenyl or norbomenylethyl groups. For example, the resin may be aPDMS tethered and end-capped with NBE groups according the followingstructure:

where n=5-5000, for example 27-1590, and m=1-100, for example 1-10. Inan exemplary embodiment of the present invention, the resin systemincludes at least one PDMS tethered and end-capped with NBE groups.

Yet another category of oligomers and/or polymers that may be used incompositions of the present invention include tri- or quadri-functionaloligomers or polymers having a >20 wt. % linear siloxane backboneend-functionalized or end-capped with an olefin group curable by ametathesis reaction, such as cycloalkenyl groups, for example norbomenylor norbornenylethyl groups. An example of such polymer isquadri-functional PDMS, end-capped with NBE groups.

By way of further example, the resin system may comprise both thetelechelic oligomer or polymer and the tethered oligomer or polymer,each functionalized with groups curable by ROMP, or may comprise thetelechelic oligomer or polymer and the tethered oligomer or polymer andthe quadri-functional oligomer or polymer, each functionalized withgroups curable by ROMP. Thus, the resin formulation may be varied toobtain desired physical properties in the uncured and cured material.

The cycloalkenyl functionalized PDMS resins that are cured via ROMP havea higher hydrocarbon content than the vinyl functionalized PDMS resinsthat are used in hydrosilation reactions. The higher hydrocarbon contentmay lead to a lower dielectric constant, which is desirable for manyelectronic applications.

In addition to the above category of oligomers and polymers, theolefin-containing substrate may comprise any othercycloalkenyl-functionalized oligomers or polymers that may undergopolymerization via ROMP mechanism, such as reactive cycloolefins, forexample DCPD. Acyclic olefin-functionalized compounds that may undergoacyclic diene metathesis polymerization are also contemplated.

In another embodiment of the present invention, the olefin-containingsubstrate may comprise a base resin as set forth in commonly-owned,co-pending U.S. patent application Ser. Nos. 11/276,270 and 11/276,273,each filed on Feb. 21, 2006, the disclosures of which are incorporatedherein by reference in their entirety as if completely set forth hereinbelow.

The composition of the present invention contemplates a catalyst pasteand base paste that upon mixture with one another, form a curablepaste/paste system in which the metathesis reaction proceeds. Generally,in this system, the catalyst paste comprises the metathesis catalyst forinitiating polymerization, and a solvent for the catalyst that ismiscible or dispersible with the base paste and that does not interferewith the metathesis reaction. The solvent may be, for example,3-phenyl-heptamethyl-trisiloxane or an alkylmethylsiloxane-arylalkylmethylsiloxane copolymer such as a 45-55%hexylmethylsiloxane/45-55% 2-phenylpropylmethylsiloxane copolymer with aviscosity of 1250 csk. Another exemplary solvent is a phenyltrimethicone such as SilCare® 15M40 (Clariant GmbH, Sulzbach, Germany).Yet another exemplary solvent is a partially phenyl substitutedpoly(dimethylsiloxane), such as Dow Corning Fluid 556. The base pastegenerally comprises the olefin-containing substrate that is curable viaROMP or other metathesis reaction, and the reaction control agent. Thecomposition may further include filler systems and/or optional additivessuitable for the particular application, such as pigments orsurfactants, that do not interfere with the reaction. The compositionmay also include additional curing agents, such as photointiators andphotocoinitiators, to provide an additional curing mechanism besides themetathesis catalyst.

The compositions of the present invention may be used to replacehydrosilation reaction systems using platinum catalysts and dual resinsystems. The metathesis reaction is a homo-reaction using a single resinsystem, which simplifies the formulation, for example using theNBE-functionalized PDMS resins in combination with a ruthenium carbenecomplex catalyst. The compositions of the present invention providetwo-part cured elastomers that function well as dental impressionmaterials, for example. The compositions of the present invention havegood air stability as well as high catalyst activity so as to providethe longer storage time in air that is desired by dental professionals.These benefits are achieved using a catalyst with low sulfur sensitivitycompared to platinum hydrosilation catalysts, which is a furtheradvantage when these compositions are used in the oral cavity asimpression materials where latex gloves containing sulfur impurities andother medicaments have previously been known to deactivate catalysts.

The reaction control agent is incorporated into the base paste, to slowthe ROMP rate upon mixing of the catalyst paste and base, therebyincreasing the working time of the resin before cure, and even toprevent completion of the ROMP in the absence of an elevated temperatureabove the mixing temperature or in the absence of exposure to light. Thepresence of the reaction control agent provides a working time aftermixing that is in a usable range for dental impression materials. Whilenumerous retarders are known for use with the platinum catalysts in thehydrosilation mechanism, unexpectedly, some of the most common of themare not effective with the ruthenium carbene catalysts in the ROMPmechanism. However, tetraallyl silane (TAS), for example, has been foundto provide significantly increased working time. Similarly, othercompounds having a Group 14 central atom and one or more ligands havinga hydrocarbon fragment and carbon-carbon double or triple bond are alsoexpected to be effective.

EXAMPLES

Various resins were formulated and tested and their properties comparedto that of two commercial dental impression materials. While thecommercial products are mixed with a 1:1 base/catalyst ratio, the resinsof the present invention were mixed with a 4:1 ratio. It may beunderstood that other ratios may be used. A telechelicpolydimethylsiloxane (PDMS) end-capped with norbornenylethyl groups wasused in the base paste, with n=243 as shown below:

The reaction control agent used was tetraallyl silane (TAS). The basepaste formulation is provided below in Table 1: TABLE 1 Base PasteComposition (wt. %) PDMS resin end-capped with norbornenylethyl 60.95 −x groups (n = 243) Reaction Control Agent x Calcium SilicateWollastonite (2-10 μm) 20.5 Sub-micron Silica 18.0 Surfactant 0.50Pigment 0.05 Total 100

Three catalysts, Catalysts A, B, and C, of the following formula wereused in the catalyst paste, each obtained from Materia, Inc., Pasadena,Calif., under Product Nos. C627, C629 and C657, respectively:

As described above, for Catalyst A, R⁴ is isopropyl and c is H; forCatalyst B, R⁴ is methyl and c is methoxy; and for Catalyst C, R⁴ isethyl and c is ethoxy. The catalyst component was formulated bydissolving it in a partially phenyl substituted polymethylsiloxane, inparticular, Dow Corning Fluid 556, followed by compounding with fillers.The catalyst paste formulation is provided in Table 2: TABLE 2 CatalystPaste Composition (wt. %) Dow Corning Fluid 556 39.955 Calcium SilicateWollastonite (2-10 μm) 45 Sub-micron Silica 15 Catalyst 0.045 Total 100

The base paste and catalyst paste were mixed at ambient temperature. Thephysical properties of dental impression materials prepared with theabove base pastes and catalyst pastes and the two commercialcompositions are provided in Table 3. The numbers in parenthesesindicate standard deviation.

The desired work time (WT) and set time (ST) ranges for dentalimpression materials are 90-140 sec for WT and less than 300 sec for ST.The work times detailed in Table 3 show that different TAS levels foreach type of catalyst may be necessary to produce the desired WT and STranges. The physical properties of the resins of the present inventionwere similar to the commercial compositions, and these properties can befurther altered by altering the type of filler and the extent of fillerloading.

After Test Resin 1 was allowed to cure at room temperature, thecomposition was further subjected to post-curing for 1 hour at 175° C.to ascertain the affect of subsequent post-curing on the physicalproperties of the compositions of the present invention. The post-curehad the benefit of significantly increasing the tensile strength to 3.75(0.14) MPa and the tear strength to 7.6 (0.2) N/mm. The decrease inelongation to 222 (19) % and the increase in hardness to 58 (1) wererelatively small.

Table 4 provides the WT and ST for each catalyst controlled with thesame TAS content, as well as with no addition of the TAS reactioncontrol agent. Without the addition of a reaction control agent, thecompositions quickly proceed toward a complete cure and exhibit a WT farbelow the practical level necessary for use as a dental impressionmaterial. With 1500 ppm of a TAS reaction control agent, the metathesisreaction by Catalyst A was controlled to the desired WT and ST rangesfor a dental impression material. For the metathesis reactions byCatalysts B and C, the reaction was slowed significantly by the 1500 ppmlevel of TAS compared to no TAS addition. However, for practicalpurposes, when used as a dental impression material, a lower TAS contentshould be used such that the WT and ST are not longer than desired.TABLE 3 Imprint II Garant HB Take 1 Tray Heavy Body (Kerr) (3M ESPE)Test Resin 1 Test Resin 2 Test Resin 3 Catalyst Pt-based Pt-based A B CMixing Ratio 1:1 1:1 4:1 4:1 4:1 TAS (ppm, resin basis) N/A N/A 1500 250100 Consistency (mm)  28 (1)   31 (1)   31 (1)   32 (1)   32 (1) ManualWork Time WT (sec) 118 185  90  92 104 Set Time ST (sec) 242 341  174233 265 Tensile Strength (MPa, Die D)  3.0 (0.7)  3.2 (0.2) 2.41 (0.12)2.07 (0.27) 1.95 (0.20) Elongation (%, Die D) 234 (73) 98.1 (9.6)  229(16)  166 (22)  136 (24) Hardness, Shore A (Room T)  52 (1)   54 (1)  54 (1)   51 (1)   54 (1) Tear Strength (N/mm)  6.8 (0.2)  4.4 (0.3) 5.1 (0.1)  3.6 (0.3)  4.1 (0.1)

TABLE 4 Comparative Comparative Comparative Test Resin 1 Test Resin 4Test Resin 5 Resin 6 Resin 7 Resin 8 Mixing Ratio 4:1 4:1 4:1 4:1 4:14:1 Catalyst (224 ppm, resin A B C A B C basis) TAS (ppm, resin basis)1500 1500 1500 0 0 0 Manual Work Time (sec) 90 153 235 8 11 12 Set Time(sec) 174 435 550 24 30 42

Table 5 shows the effect of exposure to elevated temperatures duringstorage on a composition of the present invention compared to acomposition using a catalyst containing a phosphine ligand. Test Resin 9of the present invention utilized Catalyst A in the catalyst paste.Comparative Resin 10 used a catalyst having the following structure:

obtained from Materia, Inc. under Product No. C848. The base andcatalyst pastes were prepared as described above. Prior to mixing thepastes together, paste samples for preparing each resin type were storedin an oven at an elevated temperature above ambient temperature, namely61° C., for 4 days, 8 days, or 15 days. For comparison, paste sampleswere also mixed together at ambient temperature without storing atelevated temperature. The WT and ST were then measured for eachcomposition. TABLE 5 Test Resin 9 Comparative Resin 10 Mixing Ratio 4:14:1 Catalyst (ppm, resin basis)  224 448 TAS (ppm, resin basis) 1290  0Manual Work/Set Time (sec)  90/165 153/435 25° C. Initial ManualWork/Set Time (sec) 136/296  74/261 61° C., 4 days Manual Work/Set Time(sec) 128/282 No Cure 61° C., 8 days Manual Work/Set Time (sec) 184/430No Cure 61° C., 15 daysThe catalyst used in Resin 10 is far more sluggish at room temperaturethan Catalyst A used in Test Resin 9, which is expected, since CatalystA is designed to have higher activity as a metathesis catalyst. CatalystA is also more stable than the other catalyst, which can be attributedto the presence of the phosphine ligand (PCy₃) in the other catalyst.Phosphines easily oxidize in the presence of atmospheric oxygen to givethe corresponding phosphine oxide, which cannot function as a ligand forthe ruthenium carbene complex. The result is oxidative degradation ofthe catalyst complex, and ultimately, the inability of the catalyst tocure the composition. Test Resin 9 is capable of being stored longerwithout degradation and deactivation of the catalyst. Thus, in anexemplary embodiment of the present invention, the catalyst isphosphine-free.

By using a reaction control agent in the formulation in combination witha high activity catalyst free of phosphines, it is believed that desiredwork times and set times can be achieved at room temperature, and thecatalyst paste may be stored for a longer period before the catalystloses its ability to cure the composition. Also, some reaction controlagents may be effective to prevent the metathesis reaction from eitherbeing initiated or from being completed absent application of anelevated temperature greater than the mixing temperature or exposure tolight within a certain time window. In these embodiments, the metathesisreaction should be completed by heat or light curing before the catalystloses its potency to metathesize the olefinic compound, i.e., before thecatalyst deactivates.

The compositions of the present invention are particularly contemplatedfor use as dental impression materials. However, the invention is not solimited. Other potential uses for compositions of the present inventioninclude automotive applications, electric/electronics applications andflexible adhesives therefor, electro and appliances, medicalapplications, textile applications, and other miscellaneousapplications. By way of example and not limitation, automotiveapplications may include: distributor caps, cable bushings, loudspeakercovers, housing seals, bellows, plug seals, spark plug boots, ventflaps, grommets for weather packs, central door locker membranes,o-rings, gaskets, bushings, boots, and combined elements withthermoplastics. By way of example and not limitation,electric/electronics applications may include: sockets for antennas,terminals, plug connections, conductors (overvoltage), insulators (highvoltage), housing seals, reinforced insulating hoses, vibration dampers(collectors), switch membrane covers (damp room switches), watch seals,insulating parts for hot adhesive guns, key pads for computers andtelephones, anode caps, insulators and surge arresters, diaphragms,grommets, cable seals, and covers for switches. By way of example andnot limitation, electro and appliance applications may include: smallseals, cable bushings, reinforced insulating hoses, lamp seals,appliance feet, membranes, o-rings, diffuser for hair dryers, gasketsfor faucets, gaskets for pressure cookers, detergent seals for dishwashers, parts for coffee and espresso machines, coated glass fiberhoses for electric stoves, and water diffuser for shower bath. By way ofexample and not limitation, medical applications may include: seals formedical appliances, syringe plungers, breast nipple protectors, baseplates (dental), inflating bellows, catheters, instrument mats,sterilization mats, O-rings for dialysers, earplugs, pipette nipples,catheter holders, cannula protection sleeves, nose clamps, valves andbellows for respirators, baby bottle nipples, baby pacifiers, stoppers,respiratory masks, Foley catheters, electrodes, cements used inorthopedic surgery such as for bone cementation and vertebroplastyprocedures, parts for dental applications, and parts for medicalequipment. By way of example and not limitation, textile applicationsmay include: textile coating for conveyor belts, tents, compensators andtechnical applications, sleeves for electrical and heat insulation, heatreflecting fabrics for steel worker's coats, airbag coating, andprinting inks. By way of example and not limitation, miscellaneousapplications may include: swimming goggles, snorkels and mouthpieces forsnorkels, elements for sport shoes, diving masks, swimming caps,respiratory devices, photocopier rolls and butcher's gloves. All of theforegoing are intended to be exemplary uses for the compositions of thepresent invention and are not intended to limit the invention in anyway.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative method andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the scope or spirit ofthe general inventive concept.

1. A composition capable of undergoing a metathesis reaction upon mixingits components, the components comprising: an olefin-containingsubstrate capable of undergoing a metathesis reaction; a carbene complexcatalyst capable of initiating the metathesis reaction in thecomposition, wherein the catalyst has the structure:

wherein: M is ruthenium or osmium, X is an alkylidene ligand withbasicity higher than that of tricyclohexylphosphine (PCy₃), Z is oxygen(O) or sulfur (S) X² and X³ are either the same or different and are anyanionic ligand, and R⁴, R⁵, a, b, c, and d are the same or different andare each a linear, branched, cyclic or polycyclic organic residueoptionally containing siloxane groups (Si—O—Si) and optionallycontaining heteroatoms selected from the group consisting of B, N, O,Si, P, and S; and at least one reaction control agent for slowing theprogress of the metathesis reaction after mixing the compositioncomponents and having the structure:

wherein: G is selected from the group consisting of: L³,

L is a hydrocarbon fragment containing a double or triple bond, L¹-L⁹are each independently selected from the group consisting of L, alkyl,aryl, aralkyl or haloalkyl, A is a Group 14 atom, n=0-20, and m=0-20. 2.The composition of claim 1 wherein M is ruthenium; X is1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene; X² and X³ arechlorine atoms; Z is oxygen; R⁴ is isopropyl, ethyl or methyl; a, b, c,and d are each either hydrogen, ethoxy or methoxy; and R⁵ is hydrogen.3. The composition of claim 1 wherein the X has the structure:

wherein Mes is mesityl and R′ is hydrogen or phenyl.
 4. The compositionof claim 1 wherein the X has the structure:

wherein Mes is mesityl.
 5. The composition of claim 1 wherein thecatalyst is free of phosphines.
 6. The composition of claim 1 wherein Lis a hydrocarbon fragment containing an allyl group, a vinyl group, anethynyl group or a propargyl group.
 7. The composition of claim 1wherein A is silicon.
 8. The composition of claim 1 wherein the at leastone reaction control agent includes tetraallyl silane ortetraallyloxysilane.
 9. The composition of claim 1 wherein theolefin-containing substrate includes at least one oligomer or polymerhaving a >20 wt. % linear siloxane (Si—O—Si) backbone functionalizedwith cycloalkenyl groups capable of undergoing a metathesis reaction.10. A composition capable of undergoing a metathesis reaction uponmixing of its components, the components comprising: anolefin-containing substrate comprising at least one oligomer or polymerhaving a >20 wt. % linear siloxane (Si—O—Si) backbone functionalizedwith olefin groups capable of undergoing a metathesis reaction, whereinthe at least one oligomer or polymer is selected from the groupconsisting of: a telechelic oligomer or polymer end-capped with thegroups, an oligomer or polymer tethered and end-capped with the groups,a tri-functional oligomer or polymer end-capped with the groups, and aquadri-functional oligomer or polymer end-capped with the groups; aruthenium carbene complex catalyst capable of initiating the metathesisreaction in the composition, wherein the catalyst has the formula:

wherein: M is ruthenium or osmium, X is an alkylidene ligand withbasicity higher than that of tricyclohexylphosphine (PCy₃), Z is oxygen(O) or sulfur (S) X² and X³ are either the same or different and are anyanionic ligand, and R⁴, R⁵, a, b, c, and d are the same or different andare each a linear, branched, cyclic or polycyclic organic residueoptionally containing siloxane groups (Si—O—Si) and optionallycontaining heteroatoms selected from the group consisting of B, N, O,Si, P, and S; and at least one reaction control agent for slowing theprogress of the metathesis reaction after mixing the compositioncomponents and having the structure:

wherein: G is selected from the group consisting of: L³,

L is a hydrocarbon fragment containing an allyl group, a vinyl group, anethynyl group or a propargyl group, L¹-L⁹ are each independentlyselected from the group consisting of L, alkyl, aryl, aralkyl orhaloalkyl, A is a Group 14 atom, n=0-20, and m=0-20.
 11. The compositionof claim 10 wherein the olefin groups are norbomenyl groups ornorbornenylethyl groups.
 12. The composition of claim 10 wherein theolefin-containing substrate includes polydimethylsiloxane tethered andend-capped with norbomenylethyl groups and having the formula:

where n=5-5000, and m=1-100.
 13. The composition of claim 10 wherein theolefin-containing substrate includes telechelic polydimethylsiloxaneend-functionalized with norbomenylethyl groups and having the formula:

wherein n=5-5000.
 14. The composition of claim 10 wherein M isruthenium; X is 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene; X²and X³ are chlorine atoms; Z is oxygen; R⁴ is isopropyl, ethyl ormethyl; a, b, c and d are each either hydrogen, ethoxy or methoxy; andR⁵ is hydrogen.
 15. The composition of claim 10 wherein the X has thestructure:

wherein Mes is mesityl and R′ is hydrogen or phenyl.
 16. The compositionof claim 10 wherein the X has the structure:

wherein Mes is mesityl.
 17. The composition of claim 10 wherein thecatalyst is free of phosphines.
 18. The composition of claim 10 whereinL is a hydrocarbon fragment containing an allyl group, a vinyl group, anethynyl group or a propargyl group.
 19. The composition of claim 10wherein A is silicon.
 20. The composition of claim 10 wherein the atleast one reaction control agent includes tetraallyl silane ortetraallyloxysilane.
 21. A curable composition comprising: anolefin-containing substrate comprising at least one oligomer or polymerhaving a >20 wt. % linear siloxane (Si—O—Si) backbone functionalizedwith cycloalkenyl groups capable of undergoing a metathesis reaction; aruthenium carbene complex catalyst capable of initiating the metathesisreaction in the composition, wherein the catalyst has the structure:

wherein R⁴ is isopropyl, ethyl or methyl, and c is hydrogen, methoxy orethoxy; and a reaction control agent for slowing the progress of themetathesis reaction, wherein the reaction control agent is tetraallylsilane or tetraallyloxysilane.
 22. The composition of claim 21 whereinthe cycloalkenyl groups are norbornenyl groups or norbornenylethylgroups.
 23. The composition of claim 21 wherein the olefin-containingsubstrate includes polydimethylsiloxane tethered and end-capped withnorbomenylethyl groups and having the formula:

where n=5-5000, and m=1-100.
 24. The composition of claim 21 wherein theolefin-containing substrate includes telechelic polydimethylsiloxaneend-functionalized with norbomenylethyl groups and having the formula:

wherein n=5-5000.